Control apparatus



June 23,. 1942. E. D. LILJA comnox, APPARATUS Filed Sept. 12, 1939 2 Sheets-Sheet l INVENTOR a i 3 Ti D r a El ATTORN J1me- 1942- E. D. LILJA 2,287,045

CONTROL APPARATUS Filed Sept. 12, 1939 2 Sheds-Sheet 2 Ed INVEItXb'OR-L l cu z, (1 BY 5 J ATroRNE Patented June 23, 1942 common APPARATUS Edgar D. Lilia, Rockford, 111., assignor to Barber- Colman Company, Rockford, 11]., a corporation of Illinois Application September 12, 1938, Serial No. 229,559

12 Claims.

This invention relates generally to automatic apparatus for governing acondition, as a chemical, physical, or electrical condition, by modulating the position of a regulating member such as a valve, a damper, a rheostat, a speed changer, or the like. More particularly the invention relates to controls of the character in which a primary response occurs in proportion to the degree oi deviation of the controlled condition from the value desired to be maintained and is followed by a slow secondary response causing suillcient further correcting movement of the regulating member to eflect complete restoration of the controlled condition to. the desired value.

The primary object of the invention is to provide a novel control of the above character-which is simple and inexpensive in construction, which is reliable in operation, which enables the control condition to be maintained with a high degree of uniformity, and which permits the mechanism for producing the secondary response above referred to be located remotely from the condition responsive means as well as the regulating member.

Another object is to provide a resetting-proportioning control having means which acts uniformly and with extreme sensitivity in initiating and producing the secondary response of the regulating member.

A further object is to provide such a control in which the proportioning and resetting actions are produced through the medium of a relay, the balance of which is upset mechanically in response to detected condition deviations.

The invention also resides in the novel character of the mechanism for controlling the secondary or restoring movement of the regulating member.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings. in which- Figure 1 is a schematic view and wiring diagram of a control embodying the present invention.

Fig. 2 is a similar view of a modified form of the control.

The invention is applicable to the control of various kinds of regulating members for maintaining a wide variety of conditions. For convenience of illustration, however, the invention is shown in the drawings and will be described as applied to the control of one typical form of temperature changer for maintaining a uniform not intendto limit the invention by such exemplary disclosure but aim to cover all modifications and alternative constructions and uses falling within the spirit and scope of the invention as expressed in the appended claims.

Referring first to Fig. 1, the temperature changer shown is a. heater of the so-called unit ventilator type comprising a casing 3 through which fresh or recirculated air or a mixture of both is drawn by a power driven blower l and discharged from the casing outlet 5 into the room or space 6 to be conditioned after all or part of the air has passed over an exchanger in the form of a heating radiator 1 containing suitable heated fluid supplied from a source 1.

The proportion of the air current subjected to the heating coil is determined by the position of a regulating member in the form of a damper 8 pivoted at 9 and swingable from the full-cooling position against a stop 9 in which all of the air is diverted around the coil 1 through a by-passage Hi to a full-heating position against a stop ill in which all of the air is directed through the coil. Thus, the conditioning capacity of the heating apparatus and therefore the temperature of the delivered air will vary progressively with changes in the position of the damper.

Herein, the damper is arranged to be oscillated varying distances back and forth with a graduated movement by a reversible power driven operator herein shown as comprising an electric motor ll operating through speed-reduction gearing II" to drive a main operating shaft 12 connected by suitable cranks and links to the damper pivot. Preferably, the motor is of the shaded pole induction type having a winding l3 constantly energized from a low voltage source H of alternating current and a rotor l5 arranged to turn clockwise and counter-clockwise respectively according to which of two sets of shading coils i6 and I! is short-circuited, the rotor remaining idle when both sets are opencircuited.

Themeans for detecting deviations in the con dition being controlled, that is, the space temperature, from the value desired The main-- tained, comprises in the present instance a thermostat l8 preferably of the simple double switch type such as is commonly used electrical control systems of the floating The temperature responsive element l9 oi" the thermostat comprises two strips l9 and E9 of metal having different coeiiicients of expansion and joined totemperature in a space to be conditioned. I do gether so as to warp in opposite directions with preferably substantially opposite changes in the ambient temperature. The element is supported from one end and carries at its other end a contact 2| movable between two limit positions against stationary con-' tinuously during operation of the heating system and the degree of energization is governed, in the present instance, by the combined action of two independently operable potential dividing tacts .22 and 23 and. cooperating therewith to 5 rheostats 36 and 31. These comprise resistance .minal of the shading coils, and conductors 21 and 28 extend from the contacts 22 and 23 terminals or the; coils l6 and. M. The limit switches 29 and 30 are opened by cams 3| and elements 38 and 39 respectively engaged by wiper arms 40 and 4|, the former being fast on the shaft I2 so as to'be moved in unison with the damper 8. The terminals of the resistance 38 through limit switches 29 and 30 to the insulated are C t d to. t Current Source 14 y @011- ductors 42 and 43, the latter including a fixed resistance 44. Conductors 45 and 46, the latter thev contacts 22 and 23 are spaced as close to- *The wiper arms "and 4| are connected to op- .gether as is practicable whileat the same time maintainingclearance between the cooperating switch contacts in the neutral position of the tongue in which both switches are open.

posite terminals of the solenoid winding 33 by conductors 48 and 49.

With the above arrangement, the voltage impressed on the solenoid at any time may be con- When the temperature of the thermostatic 2 0 sidered as the line voltage minus the drop in against the contact .23 and. closure of the switch voltage across the resistance 38 from the con- "ductor 42 to the arm 40 and through the re-,

sistance 39 from wiper arm 4| to drop across the resistance 39 between the arm 4| and the short-circuits the shading coils l6 whereupon 5 terminal 5|, .Assuming that the arm 4| remains movement of the damper 8 toward full-heating position isinitiated. This movement continues until the switch 25 or the limit. switch opens after which the position of the damper will restationary. the voltage impressed on the solenoid 33 will increase progressively as the arm 40 wipes across the resistance 38 during counterclockwise rotation of the damper operating shaft vl2 in main fixed so long as the thermostat tongue .re- 30 response to short-circuiting of the shading coils mains in the neutral position shown with both switches open; Movement of the tongue l9 to heat-decreasing position against the contact 22 as a result of a rise in temperature above the IS by closure of the thermostat switch 25. The resulting increase in the force exerted by the solenoid imposes more and more tension on the thermostatic element resulting in acorrespond prevailing control point closes the switch 24. ing lowering of the thermostat control point.

This short-circuits the coils and causes the motor to' operate ina direction to increase the proportion of the air by-passed around the heating coil.

The invention contemplates a' primary re-' sponse of the control which will change the position of the regulating member or damper 8 to Similarly, the energizing current decreases progressively as the shaft l2'turns clockwise as it will while the thermostat switch 24 is closed and correspond with the changed value of the room equilibrium position for each different room tem temperature. Such true-proportioning action is,

means for varying the effective control point of the roonrthermostat '|8 through a comparative-' iy narrow temperature range pregressively and instantaneously with perature. The value of the resistance 38 is copreferably efiected through the provision of 5 o'rdinated with the construction, of the solenoid and thermostatic element in a manner such that the range through which the control point of the thermostat will be shifted in the movement of the rheostat arm as the damper moves throughchanges in the position of the regulating mem- 50 out its range will be as small as practicable her. In the present instance, this means comprises an adjusting relay including a magnet 33 of the solenoid'type mounted adjacent but in-. sulated from the thermostat and having an -ferent operating conditions.

without the attendant danger of producing obiectionable hunting of the damper in the establishment of its equilibrium positions under dif- In systems of the armature 34 connected through the medium of 5 character shown, this range may, for example,

a contractile spring 35 to the tongue I9 of the thermostat. The solenoid exerts on the tongue a light mechanical force determined by its degree of energization and acting to vary the conbe approximately three degrees.

As an incident to repositioning of the regulating member in proportion to a deviation of the controlled condition from the desired value or so trol point of the thermostat, that is to say, to long .as the controlled condition deviates from cause the thermostat tongue 19 to be disposed between the contacts 22 and 23 at different ambient temperatures. Otherwise stated, the thermostat and the solenoid constitute a magnetic a predetermined desired value, the operation of mechanism is initiated to produce the seconda y response of the control, that is, to cause enough further movement of the regulating member to relay which is balanced when the contact 2| \restore the controlled condition to the desired or stands between the contacts 22 and 23. .It may be unbalanced or rebalanced electrically by varying the degree of energization of the solenoid. Or the relay may be unbalanced mebalanced value. Herein, this mechanism is struc- :turally separate and mechanically disconnected from the damper operator and the thermostat |8 and operates to actuate the rheostat 31 in a chanically by the condition responsive means or 7 manner such as to shift .the control point of the with abient temperature changes is applied directly to the relay contact 2|.

The-solenoid 33 is maintained energized conregulating device, the thermostat control point thermostat in a direction reverse to and at a rate substantially slower than that resulting from movement of the damper. Such readjustment continues until, for'the changed position of the has been restored precisely to a fixed value corresponding to the temperature condition desired to be maintained in the space being heated.

Preferably, such slow actuation of the rheostat 31 is effected by a motor driven operator 55 comprising a reversible shaded pole induction motor 56 of the same construction as the motor II and connected through appropriate speed reduction gearing to a shaft 58 on which the wiper arm 4! is fast. By proportioning the gearing 51 or by adjustment of a fluid pump 59 driven by the motor 56, the speed of the latter may be adjusted so that the shaft 58 operates at only a fraction, for example, one-tenth, of the speed of the damper operating shaft l2.

' The motor 56 is controlled by a balanced magnetic relay 60 comprising a solenoid 6| similar in construction to the solenoid 33 and having a winding connected by conductors 62 and 63- to the conductors 48 and 49. The solenoid is thus interposed in parallel with the solenoid 33. The armature 64 of the solenoid is joined through a conical contractile spring 65 to a leaf spring 66 anchored at one end and carrying a contact 61 at its free end cooperating with contacts 68 and 69 to form two switches 10 and H. Conductors 72 and 13 connect the contacts 68 and 69 to the insulated terminals of the shading coils H and while the common terminals of the latter are connected to the spring tongue 66 by a conductor 76. The arrangement is such that when the switch l0 is closed. the coils 14 are shortcircuited and the motor operated in a direction to swing the arm 4| clockwise thereby increasing the voltage applied to the solenoids 33 and 6!. Reverse movement of the arm and a decrease in voltage occurs when the coils 75 are shortcircuited by closure of the switch H. When the prevailing pull of the solenoid 6| is just balanced against the tension of the spring 66, the contact 6! stands in mid-position. both switches then being open and the motor 56 idle.

Being in parallel, the solenoids and 61 are always energized to the same degree determined by the combined condition of the rheostats 36 and 31. The adjustment of the relay 60 is such that it is balanced when energized by a current of the magnitude required to maintain the thermostat l8 balanced when the controlled con dition, that is, the air temperature around the thermostatic element i9. is at its value desired to be maintained. In other words. the relay 60 operates to detect deviations in the thermostat control point from its normal or desired value, and to close the switches '10 and "H selectively when such point rises above and falls below such value. The operation of the motor 56 resulting from such switch closure is in a direction such as to cause the rheostat 37 to restore the desired normal control point of the thermostat.

It will be observed that the power operator 55, the rheostat 31, and the relay 60 are mechanically disconnected from the damper operator and the control instrument including the adjusting relay 33. All of the connections between these elements are electrical which permits them to be located remote from each other as may be required by the characteristics of the installation in which they are used.

In explaining "the operation of the control above described, it will be'assumed that the controlled condition desired to be maintained is a. space temperature of 70 degrees and that the thermostat i8 is so set. When the space temperature falls below 70 degrees,'the tongue I! warps upwardly and closes the switch 25 which short-circuits the shading coils I6 causing the motor II to run in a. clockwise direction. The shaft I2 is turned counter-clockwise moving the damper 6 toward full-heating position. The

simultaneous movement oi the wiper arm 40 results in an increase in the voltage impressed on the solenoid 33 and a corresponding increase in the solenoid pull, causing the switch 25 to open and stop the motor H when the damper has moved through a distance proportional to the amount the room temperature has fallen below 70 degrees. r

The increased excitation of the solenoid 6! which occurs simultaneously with that of the solenoid 33 results in closure of the switch H which short-circuits the shading coils 15 causing the motor 56 to run in a clockwise direction turning the wiper arm ll of the rheostat 3'! counterclockwise at a comparatively slow rate. Such movement is accompanied by a slow decrease in the voltage impressed on the windings 33 and 6|, and this decrease continues until the motor 56 .s stopped by opening ofthe switch H when the relay" again becomes balanced. At this time, the

' control point of the thermostat I8 will have been restored fully to its normal value.

As an incident to such full restoration, the thermostat normally will, due to raising of the control point by the action of the rheostat 31, close its switch 25 thereby initiating further movement of the damper in the heat-increasing direction and a corresponding increase in the energizing current.

sponse or restoring action until finally the capacity of the heater will have been increased sufiiciently to bring the room temperature back to normal.

'When the room temperature rises' above normal. the switch 24 is closed short-circuiting the other shading coils I1 and driving the damper 8 in the heat-decreasing direction. At the same time, the slider 40 is moved clockwise which correspondingly decreases the solenoid voltage. The decreased pull of the solenoid 33 raises the ef fective thermostat control point so that the damper movement is interrupted at a position corresponding to the magnitude of the temperature deviation. The decreased energization of the relay 6!! causes closure of the switch 10 and short-circuiting of the coils M resulting in clockwise movement of the rheostat arm H. During the ensuing slow restoration of the solenoid voltages to normal, the damper may, due to continued high room temperature, be moved intermittently in the heat-decreasing direction, the direction of change in the solenoid energization being reversed under the control of the rheostat 36 during such movements. Finally, when the balanced condition of both the relay 33, 34, 35 and the relay 6|! has been restored following lowering of the room temperature to the desired value, operation of both motors II and 56 will be arrested, the system remaining balanced until the room temperature again deviates from normal.

As a result of the primary or proportioning action and the secondary or restoring action described above, the regulating member or damper will, in response to a deviation of the controlled conditi n from normal, quickly assume a new position which is a function of the deviation. Then, in response to' the secondary action, the damper will move slowly to a further position The cycle may be repeated I several times in the course of the secondaryre- 4 Fig, 2 shows an adaptation of theim'proved control to a system controlled by a so-called potentiometer type of condition responsive device. To simplify the description of this system, the parts common to the system shown in Fig. 1 are indicated by the same reference numbers.

In the modified system, the condition responsive device comprises a thermostatic bellows 89 operating an arm 8! to swing a wiper arm 92 across a resistance element 93. .This element and the arm 83 constitute a rheostat acting jointly with the rheostats 36 and 31 to control the energization of abalanced relay 92 having switches 94 and 95 which control the windings l1 and I6 of the damper operator in the same way as the switches 24 and 25 in the preferred form of the invention shown in Fig. 1. The relay 92 is of the same construction as the relay 60 comprising a solenoid 93 having an armature 96 connected by a spring 91 to a leaf spring 98 which carries the common contact 99 of the switches 94 and 95.

The energizing circuit for the solenoid 93 extends from the current source l4 through a conductor 84, part of the element 83, the arm 82,

a conductor 85, the solenoid winding 93, aconductor 86, wiper arm 49, part of resistance element 38, a conductor 81, wiper arm H, a part of element 39, and a conductor 88. The thermostat rheostat also controls the energization of the relay 60 independently of the rheostats 36 and 31 and to this end the winding 6| is joined by conductors 90 and 9| to the conductor 85 and to one terminal of the current source.

In operation of the modified system, the thermostatic bellows contracts on a fall in the room temperature and moves the arm 82 clockwise thereby reducing the effective resistance of the solenoid circuits. The resulting increase in the current energizing the solenoid winding 93 causes the switch 95 to close. This short-circuits the coils I6 of the motor H turning the shaft l2 counter-clockwise and increasing the rate of heat delivery. The simultaneous movement of therheostat arm 48 increases the resistance and decreases the current in the circuit of the solenoid winding 93. The damper motor continues to run until the current in the relay 92' has returned to normal whereupon the switch 95 opens. Since the movement of the rheostat arm 40 is proportional to the movement of the thermostat arm 82, the initial damper movement will be proportional to the degree of deviation of the temperature from normal.

The reduction in the effective resistance of the rheostat element 83 incident to the room temperature drop above assumed lowers the voltage applied to the relay winding 6| andcauSesthe the heat supply further and again move the rheostat 36 in a direction to reduce the current in the winding 93 and reopen the switch 95. This action may be repeated several times in response to actuation of the rheostats 36 and 31 before normal room temperature is attained.

Now, if the room temperature rises above normal, the bellows will expand and increase the effective resistance of the solenoid circuits. This in turn will cause the switch 94 to close and the motor II will drive the damper in the heat-decreasing direction during which the current in the winding 93 is increased by the rheostat 36. As before, the initial movement of the damper will be proportional to the temperature departure fromthe normal balanced value,

The movement just referred to of the thermostat arm 82 also. increases the voltage impressed on the solenoid winding 6| causing closure of the switch H and operation of the motor 56 to drive the rheostat arm 4| slowly in a counterclockwise direction. This decreases the current in the solenoid 93 as long as the room temperature remains above normal and results in intermittent movement ofthe faster operating damper actuator until the temperature is reduced to normal. From the foregoing, it will be seen that the modified form of control produces the desired primary response or proportioning action followed by a secondary or resetting action the same as the control shown in Fig. 1.

I claim as my invention:

1. In a system of the character described, the combination of two independently operable voltage regulators, two reversible power operators for actuating the respective regulators at different speeds, balanced magnetic relays individually v controlling the respective operators and'having ber, a magnetic relay, control means for said operator responsive to changes in said condition and in the energization of said relay, a voltage regulator actuated in unison withsaid member and controlling the energization of said relay, an independent magnetic relay variably energized in accordance with changes in the ener- =gization of said first relay, means controlled by said second relay and operating in response to a deviation in the energization of said first relay from a predetermined normal value to cause restoration of the energization of the first relay to such normal value at a rate substantially slower than the rate of change of energization of the first relay in response to changes in the position of said member.

3. In a system for maintaining a uniform condition, the combination of a regulating member movable to modulate said condition, a reversible power driven operator for actuating said member, a magnetic relay, control means for said operator responsive to changes in said condition and in the energization of said relay, a volt-age regulator actuated in unison with said member and controlling the energization of said relay, a magnetic relay variably energized in accordance with changes in the energization of said first re- I lay, mean controlled by said second relay operating in response to a deviation in the energization of said first relay from a predetermined normal value to restore the energization to such normal value at a rate substantially slower than the rate of change of energization of the first relay in response to changes in the position of said member, said second relay and said last mentioned means constituting a unit structurally separate from said operator and first relay but associated therewith through electrical connections. i

4. In a system for maintaining a uniform condition, the combination of a regulating member movable to modulate said condition, two magnetic windings, switching means controlled by one of said windings and also responsive to changes in said condition, a power driven 'operator controlled by said switching means to cause condition-increasing and condition-decreasing movements of said member in response to opposite changes in the position of said switching means from a normal balanced position, two

point, of the instrument, a magnet operatively associated with said instrument and varyingthe control point thereof to correspond to the degree of magnet energization, two independently operable voltage regulators controlling the energization of said magnet, one of said regulators being actuated in unison with the movements of said member, a reversible power driven operator for actuating said other voltage regulator at a slower rate than the first regulator, a balanced magnetic relay-in parallel with said magnet and controlled by said regulators, and means actuated by said relay and controlling the direction and extent of operation of said operator to restore a predetermined normal degree of energization of said magnet and relay.

7. The combination of three rheostats connected in series relation, condition responsive voltage regulators each controlling the energization of said windings, one of saidtregulators being movable in unison with said member to re-' store the balanced position of said switching means following a change in said condition, a second reversible power operator for actuating the second voltage regulator to change the energization of said windings at a slower rate than said first regulator, and switching means controlled by said second winding and operableto cause operation of said second operator in opposite directions with opposite deviations in the energization of the second determined balanced value, the direction of variation of the second operator being such as to restore the balanced condition of said second switching means,

5. In a system for maintaining a uniform condition, the combination of conditioning apparatus including a regulating member movable back and forth to increase and decrease said condition, an instrument controlling said member to cause condition-increasing and condition-decreasing movements thereof when said condition ialls below and rises above the control point of said instrument, a magnet operatively associatedwith said instrument and acting to vary the control point of the instrument to correspond to the degree of energization of the magnet, two structurally separate and mechanically disconnected voltage regulating means governing the energization of said magnet and each having a control element movable to vary the energization of said magnet, means for operatingone 01. said elements in unison with the movements of said member, an independently operable electric motor arranged to operate the other of said control elements at a speed substantially slower than the speed of actuation of the first control element, and means mechanically disconnected from said magnet and said member for causing operation of said motor in opposite directions in response to opposite deviations in the energization of said magnet away from a predetermined balanced value.

6. In a system for maintaining a uniform condition, the combination of a regulating member winding from a premovable back and forth to increase and decrease condition falls below and rises above the control means actuating one of said rheostats, relatively slow and fast operating reversible-operators respectively actuating the other rheostats, a regulating device actuated by said fast operator, a magnetic relay controlling the fast operator and controlled .by the joint action of said rheostats, and a second magnetic relay controlled only by the condition actuated rheostat.

8. The combination of a reversible power operator having a driven member adapted for actuation of conditioning apparatus, a normally electrically balanced mechanism responsive to changes in a condition to be controlled by said apparatus and controlling said operator to modulate the position of said member and in proportion to changes of said condition, a second reversible power operator controlling the balance of said mechanism to produce a slow resetting action, an electric circuit governing the direction and extent of operation of said second operator including two independent voltage regulators respectively actuated by said first and second operators.

9. The combination of a reversible power operator having a driven member adapted for actuating conditioning apparatus, a normally balanced magnetic relay governing theselective operation of said operator in accordance with the direction of un'balance of the relay, means adapted to detect changes in a condition controlled by said apparatus and acting mechanically on said relay to unbalance the same in accordance with each condition change, electrical means actuated by said operator to rebalance the relay and proportion the movements of said member in accordance witheach condition change, a second electrical means controlling the relay, and a reversible power actuator operating said second electrical means during the persistence of a deviation in said condition from a predetermined value to slowly unbalance said relay in a direction determined by the condition change.

10. The combination of a reversible power operator having a, driven member adapted for actuation of conditioning apparatus, a normally balanced magnetic relay governing the selective operation oi said operator in accordance with the direction of unbalance of the relay, means adapted to detect changes in a condition conpersistence of a deviation in a predetermined value, and

balance of said said actuator following unbalance of the relay by a condition change to further unbalance the relay at a slow rate and cause secondary positioning of said member to restore the condition to said predetermined value.

ii. The combination of a reversible electric motor operator having a driven member adapted for connection to a condition regulating device, a normally balanced magnetic relay having a movable element and switch means actuated selectively by the element in accordance with the direction of movement of the element away from a neutral position, said operator being controlled by said switch means in accordance with the direction of unbalance oi the relay and being idle when said element is in said neutral position, means adapted to detect changes in a controlled condition has been restored to said predetermined value.

condition and acting mechanically on said element to unbalance the relay in proportion to each condition change, means actuated, by said operator and acting electrically on said relay to rebalance the same, and means operating during the persistence of a deviation in said condition from a predetermined value following unbalance of the relay in response to a condition change to further unbalance the relay at a slow rate and cause secondary positioning of said member until the vary the force applied to said element to unbalance the same in the direction of and in proportion to each condition change, means actuated in the ensuing operation of said operator to rebalance the relay, and independently'acting.power actuated means operating during the persistence of a deviation in said condition from a predetermined value to further unbalance the relay at a slow rate and continue such unbalancing until the condition has been restored to said predetermined value.

EDGAR D. LILJA. 

